Note: Descriptions are shown in the official language in which they were submitted.
- WO9]/16973 2 ~ PCT/FIgl/00l3~
PIPETTE
The present invention concerns a pipet'e com-
prising a body; mounted in said body, a plurality of
mutually parallel, side-~y-side cylinders with plung-
ers, plunger rods and seats for attaching tip pieces to
the pipette, and a fork-like operating member compris-
ing a stem and a coupling member thereto connected, the
plunger rods with their plungers being connected to
said coupling member in order to be simultaneously mov-
able with the aid of an operating means that can be
connected to the operating member, the operating member
with stem, coupling member and plunger rods constitut-
ing a solid entity, advantageously Lormed substan~i211y
in a single work step, e.g. by extrusion.
- Regarding the state of art, reference is made
to the Finnish Patents No. 60137 and No. 73368. In
these references pipettes of the type described above
are disclosed, in which the plunger rods with plungers
are connected to a fork-like operating member for mov-
ing the plungers simultaneously with the aid of an
operating means connectable to the operating member.
However, problems have emerged in pipettes of this
kind, particularly as regards the mutually consistent
movement of the plungers. The plungers tend to move
inconsistently and even to seize in the cylinders. This
is due to manufacturing tolerances and to the fact that
even minor centering errors in a plunger are likely to
result in seizing, as the adjacent plunger(s) deter-
mine(s) the direction in which the coupling member, andconsequently the rest of the plunger rods and plungers,
move.
The object of the present invention is to
eliminate the drawbacks to which attention was called
in the foregoing.
It is a further object of the invention to
provide a novel serial pipette which is less complex in
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WO91/16973 2 ~ ~ 2 ~ ~ ~ PCT/FI91/0013~
design, more reliable in operation and more advantage-
ous to its manufacturing cost than any se_ial pipettes
of prior art.
Regardina the features characteri~ing the in-
vention reference is made to the claims section.
As set forth in the foregoing, the operatingmember has fork-resembling shape. The coupling member
connects with the stem substantially at right angles,
and the plunger rods connect with the coupiing member
substantially at right angles, parallelling the stem
and disposed in a row, one beside the other. Therefore,
the operating member is a solid, unitary entity which
connects on one hand with the operating means of the
pipette, e.g. a hydraulically or pneumatic211y opera~-
ing power means, and on the other hand with the plung-
ers of the pipette. By virtue of the design of said
operating means, operation of the plungers of the
serial pipette will be simultaneous and mutually con-
sistent.
As taught by the invention, the plungers are
made of resilient material and they are elastically
connected to the plunger rods.
In an embodiment of the invention the plungers
are cylindrical in shape, and they have been arranged
to abut with their outside surface against the inner
surface of the cylinder. On their outside may be formed
at least one collar-like sealing ring, and each plung-
er, with sealing ring, has been shaped in a single work
step of a single material, e.g. by extrusion moulding.
The cylinders are connected to the body advan-
tageously at both ends and immovably in their longitu-
dinal, as well as advantageously their lateral, direc-
tion.
Thanks to the invention the manufacturing of
the pipette's operating member and plungers can be
implemented in a simple, easy and inexpensive manner.
At the same time, simple and consistent operation of
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'^ W O 91/16973 2 ~ PCT/FI91/00132
the pipette is achieved, i.e., the emptying and filling
of cylinders takes place in a constant and consistent,
and reliable way. Further, thanks to the invention, the
pipette of the invention is advantageous as regards
manufacturing cost.
The invention is described in detail in the
following, with the aid of embodiment examples and re-
ferring to the attached drawing, wherein:-
Fig. l presents a pipette according to the invention,
opened and in top view,
Fig. 2 presents the pipette of Fig. 1, opened and inelevational view, and
Fig. 3 presents, in elevational view, the plunger of a
pipette according to an embodiment of the invention.
In Fig. 1 is seen a pipette according to the
invention, opened and in top view. The pipette compris-
- es a box-like body lO within which have been placed the-
cylinders 1 of the pipette, with plungers 2 and with
seats 4 for attaching tip pieces (not depicted) to the -
pipette. The pipette further comprises an operating
member 5, to which the plungers are coupled for moving
them with the aid of an operating means 6 connectable
to the operating member, such as a power cylinder.
The operating member 5 has fork-like shape.
The operating member comprises a stem 7, and to this
stem is transversally connected a rigid coupling member
8, to which the plunger rods 3 are connected. The s~em
7 is carried in the housing 10 to be movable longitudi-
nally, in the direction of the cylinders 1. The cou-
pling member 8 connects substantially at right angleswith the stem 5; similarly, the plunger rods 3 are con-
nected substantially at right angles to the coupliny
member 8. The cylinders 1 and seats 4 and the operating
member 5, with stem 7 and coupling member 8 and with
the plunger rods connected to the coupling member, are
mounted substantially in one plane so that when the
stem of the operating member moves in the direction of
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WO91/16973 ~ ~ 2 ~ PCT/FI9l/0013
the cylinders, the plungers 3 will move alon~ with the
stem Gf the operating member, by mediation of the cou-
pling member, connected to the stem of the operating
member, and of the rods. Thereby, the filling of all
cylinders and individual pipettes in a serial pipette
will be effected simultaneously, and in mutually con-
sistent manner.
In Fig. 1 is further seen a return spring 9,
disposed to move the stem 5 of the operating member,
- 10 and thereby the coupling member 8 and plunger rods 3,
and the plungers 2, away from the seats, that is, in
the filling direction.
In the embodiment her~ deplcted, the boay 10
is mainly flat, and it constitutes the housing for the
pipette. Separate cylinders l, ~ith tubular liquid pas-
sages 12 parallelling them and constituting their ex-
tensions, are provided with seats 4, which have been
pushed in sleeve fashion upon the tubular liquid
passages. The cylinders together with the seats have
been mounted in mounting cut-outs provided in the body,
so that the seats project through the apertures 13, ~he
collars 14 of the seats abutting inwardly on the rims
of the apertures, and the cylinders resting with their
opposite ends on shoulders 15 formed by the rims of
apertures in the mounting frame 16 of the body, by
radially outward projecting flanges 17 formed on the
respective ends of the cylinders. It is thus understood
that all cylinders 1 with their seats 4 are disposed in
parallel, side by side and at constant spacing in the
housing constituted by the body 10, to be substantially
immobile longitudinally, and elastically in lateral
direction.
In Fig. 3 is seen a plunger 2 conforming to an
embodiment of the invention. The plunger has been manu-
factured by extrusion of plastic raw material, mainlyin a single work step. The plunger has mainly cylindri-
cal shape and has been fitted into the cylinder.
~ ~ WO91/16973 ~(Q ~ 1$~ PCT/F191/00132
The plunger 2 is advantageously made of re-
silient, elastic plastic material. The plunger is co~n-
nected to the plunger rod 3 e.g. by friction bond, by
gluing, with threads, or in any way whatsoever; the
juncture is advantageously laterally resilient so that
plungers located side by side can become centered in
the cylinders flexibly and without seizing.
The invention is not confined to the embodi-
ment examples that have been presented: its embodiments -
may vary within the scope of ~he claims following
below.
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